A series of studies, part of a broad program of research on sleep physiology, is in progress. 1. Ventral hippocampus spike activity in cats is being examined because it may reflect certain sleep processes more sensitively than the conventional EEG. This spike tends to increase just prior to sleep, achieve greatest frequency during NREM sleep, and then decrease just prior to REM sleep or wakefulness. 2. A computer based system for automatic scoring of rat sleep is being developed. Initial results show very good agreement with visual and behavioral scoring. 3. We are studying the relationships between MMPI scores and phasic discharges of extraocular and facial muscles during sleep because these discharges may reflect otherwise inaccessible brainstem activity in humans. Initial results indicate that frequency of these discharges is associated with more pathological scores on the MMPI, although the degree of relationship is not overpowering. 4. The effect of age on the sleep EEG of rodents is under investigation. Results to date indicate that, like humans, mice tend to lose sleep related, large amplitude delta waves in advanced age, but rats do not. 5. For evidence relevant to the energy conserving functions of sleep, we administered thyroxine, which increases metabolism, to rats. Although there was a weight decrease in spite of increased food intake, as would be expected with increased metabolism, there was no change in total sleep.